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arXiv · 1405.3479

A reducible characteristic variety in type A

Geordie Williamson
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Abstract

We show that simple highest weight modules for sl_12 may have reducible characteristic variety. This answers a question of Borho-Brylinski and Joseph from 1984. The relevant singularity under Beilinson-Bernstein localization is the (in)famous Kashiwara-Saito singularity. We sketch the rather indirect route via the p-canonical basis, W-graphs and decomposition numbers for perverse sheaves that led us to examine this singularity.

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Geordie Williamson. 2014-05-14. A reducible characteristic variety in type A. https://arxiv.org/abs/1405.3479

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